In a railcar, in general, a floor is required to have heat resistance, that is, a heat insulating property and fire resistance. In order to respond to such a requirement, conventionally in a general floor structure of a railcar, a heat insulating material is arranged on a lower surface of a structural floor. Patent Literature 1 discloses a floor structure wherein a highly-fire-resistant and incombustible heat insulating material made of glass wool and a highly-heat-insulating and moisture-retaining heat insulating material made of ceramic fiber are combined as a heat insulating material in order to improve the heat insulating property and the fire resistance. Patent Literature 2 discloses a floor structure of a laminated structure having an upper layer containing hydroxide, a middle layer providing structural strength, and a lower layer covering a lower surface, wherein a heat insulating material is formed between the middle layer and the lower layer.